Size of Midrange Drivers

Love the Maggies! Just wish they were more efficient.

TAD concentrics use a 6.5" midrange.

08-25-14: Psag
TAD concentrics use a 6.5" midrange.

Point?
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Johnnyb53 --

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Finally, the name of the game isn't just radiating area; it's air displacement. A 4.5" driver has a radiating surface of 15 sq. inches. My Mag 1.7s have a radiating surface of 456 sq. inches. Yet, a premium 4.5" midrange might have a maximum excursion of .2", which amounts to around 3 cu. in. of displacement. My big panel, if its excursion is .01" (I'm guessing here, but it's probably in the ballpark), displaces about 5 cu. in. of air even though it's spread over a wider area. So two of those 4.5" midranges would displace about the same amount of air at full excursion.

This is an interesting aspect. My impressions is that it's not without audible importance how a given amount of air is moved; either "gently" via a larger area, or "forcibly" through a smaller ditto. My preference - if it is indeed explained fundamentally through this aspect - is for the former, and this goes for the whole frequency spectrum.

Moreover, the number of point sources (convering the same frequency span) is also a factor. With regards to bass (and the rest of the sprectrum), generally, I'd rather have one unit covering what two or more units equaling the same radiation are can muster.

Phusis
My impressions is that it's not without audible importance how a given amount of air is moved; either "gently" via a larger area, or "forcibly" through a smaller ditto. My preference - if it is indeed explained fundamentally through this aspect - is for the former, and this goes for the whole frequency spectrum.

And I agree with you. The larger the radiating surface, the smaller the excursion required to achieve the same SPL. A 5" midrange has about 19.5 sq. in. of radiating surface; The Magnepan 1.7 has 456, or 23 times as much. The Magnepan's microscopic excursion has a profound effect on inertial artifacts--the mechanics of acceleration, stopping, ringing, and reversing. It results in a relaxed, natural presentation.

Note the expensive and herculean efforts to reduce this in a pistonic driver: the TAD coincident drivers are made of vapor deposited beryllium--brittle, fragile, but incredibly light to minimize inertial effects.

Moreover, the number of point sources (convering the same frequency span) is also a factor. With regards to bass (and the rest of the sprectrum), generally, I'd rather have one unit covering what two or more units equaling the same radiation are can muster.

I agree here, too The miraculous thing about the Maggie 1.7 is that it speaks in such a single, coherent voice for just $2K/pair. The TADs also do it with a 6.5" coincident driver that covers 8 octaves. Its point source would have an imaging advantage over the Maggies' line source, and the upper models have more bass reach, but at a significant price difference.